scholarly journals Reducing Virus Transmission from Heating, Ventilation, and Air Conditioning Systems of Urban Subways

2021 ◽  
Author(s):  
Ata Nazari ◽  
Jiarong Hong ◽  
Farzad Taghizadeh-Hesary ◽  
Farhad Taghizadeh-Hesary
Keyword(s):  
Air Conditioning ◽  
Low Cost ◽  
Infected Individual ◽  
Virus Transmission ◽  
Mean Value ◽  
Hvac System ◽  
Transit System ◽  
Encounter Probability ◽  
Flow Effects ◽  
Air Conditioning Systems

Abstract Transmission via virus-carrying aerosols inside enclosed spaces is an important transmission mode for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as supported by growing evidence. The urban subway is one of the most commonly used enclosed spaces. The subway is a utilitarian and low-cost transit system in today’s society. However, studies are yet to demonstrate patterns of viral transmission in subway heating, ventilation, and air conditioning (HVAC) systems. To fill this gap, we performed a computational investigation of the airflow (and the associated aerosol transmission) in an urban subway cabin equipped with an HVAC system. We employed a transport equation for aerosol concentration, which was added to the basic buoyant solver to resolve aerosol transmission inside the subway cabin. This was achieved by considering the thermal, turbulence, and induced ventilation flow effects. Using the aerosol encounter probability over sampling lines crossing the passenger breathing zones, we can detect the highest infection risk zones inside the urban subway under different settings. We proposed a novel HVAC system that can impede aerosol spread, both vertically and horizontally, inside the cabin. In the conventional model, the maximum aerosol encounter probability from an infected individual breathing near the fresh-air ducts was equal to 15%. This decreased to 0.36% in the proposed HVAC model. Overall, using the proposed HVAC system for urban subways decreased the mean value of the aerosol encounter probability by approximately 79% compared to that for the conventional system.

scholarly journals Analysis of Common Problems of Noise and Vibration in Building Heating Ventilation Air Conditioning Design

2021 ◽  
Vol 283 ◽  
pp. 01051
Author(s):  
Xiaolong Ruan ◽  
Yisong Yin
Keyword(s):  
Continuous Improvement ◽  
Air Conditioning ◽  
Preventive Measures ◽  
Hvac System ◽  
Continuous Growth ◽  
Noise And Vibration ◽  
Vibration Problems ◽  
Common Problems ◽  
Air Conditioning Systems ◽  
And Control

With the continuous growth of my country's economy and the continuous improvement of the people's economic level, the demand for the design of heating, ventilation and air conditioning systems has also increased. The HVAC system is very important in the building environment. When optimizing the relevant design, it is necessary to always consider the design details of the HVAC system and adjust the integrity of the design, especially to take preventive measures in areas where noise and vibration may occur to avoid heating serious problems caused by noise and general vibration when the communication system is running. This article outlines how to avoid and control common noise and vibration problems when designing HVAC projects.

scholarly journals Comparative Analysis of Energy Consumption, Indoor Thermal–Hygrometric Conditions, and Air Quality for HVAC, LDAC, and RDAC Systems Used in Operating Rooms

2020 ◽  
Vol 10 (11) ◽  
pp. 3721
Author(s):  
Tsung-Yi Chien ◽  
Ching-Chieh Liang ◽  
Feng-Jen Wu ◽  
Chi-Tsung Chen ◽  
Ting-Hsin Pan ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Air Quality ◽  
Air Conditioning ◽  
Operating Rooms ◽  
Conventional Heating ◽  
Hvac System ◽  
Total Energy Consumption ◽  
System A ◽  
Air Conditioning Systems ◽  
Daily Total

As controlling temperature and humidity is crucial for maintaining comfort and preventing microbial growth, operating rooms (ORs) are the most energy-intensive areas in hospitals. We aimed to evaluate the energy consumption of three dehumidification air conditioning systems used in ORs and their corresponding air quality for ORs at rest. This study selected three ORs using a conventional heating, ventilation, and air conditioning (HVAC) system; a liquid desiccant air conditioning (LDAC) system; and a rotary desiccant air conditioning (RDAC) system, respectively. The indoor thermal–hygrometric conditions, air quality, and energy consumption of the ORs were monitored in this study. The median levels of relative humidity (RH) were 66.7% in the OR using the conventional HVAC system, 60.8% in the OR using the LDAC system, and 60.5% in the OR using the RDAC system. The median daily total energy consumption of the RDAC system (10.1 kWh/m2) and LDAC system (11.8 kWh/m2) were 28.12% and 16.54% lower, respectively, than that of the conventional HVAC system (14.1 kWh/m2). The PM≥0.5 levels and airborne bacterial concentrations in the ORs met the ISO 14644-1 Class 7 standard and China’s GB50333-2013 standard, respectively. The RDAC system was clearly superior to the LDAC and conventional HVAC systems in terms of energy consumption.

scholarly journals Optimization of the Electric Vehicle HVAC Duct System Based on Gradient Method

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Air Conditioning ◽  
Gradient Methods ◽  
Point Of View ◽  
Temperature Fields ◽  
Hvac System ◽  
Computational Aerodynamics ◽  
Electric Car ◽  
Air Conditioning Systems ◽  
Short Time ◽  
Initial Geometry

Our study describes the optimization of the part of heating, ventilation and air conditioning (HVAC) system of an electric car. The geometry of the air duct connected to the heater unit on one side and the dashboard on the other. From the point of view of aerodynamics, it is necessary to change the geometry of the air duct so as to minimize the loss of air pressure and ensure a more uniform flow from the exit holes to improve the efficiency of windshield heating. In order to optimize the initial geometry of the air duct, approach of using gradient methods was applied. According to the results of the study, detailed concept of optimizing the air duct of an electric car is presented. The optimized geometry was tested with the use of methods of computational aerodynamics. Calculations were made as part of the interior model of electric car with the output of temperature fields on the windshield. The results can be applied to the design of heating, ventilation and air conditioning systems of vehicles in a short time.

Significance of Temperature and Humidity Control for Agricultural Products Storage: Overview of Conventional and Advanced Options

2019 ◽  
Vol 15 (10) ◽  
Author(s):  
Muhammad Hamid Mahmood ◽  
Muhammad Sultan ◽  
Takahiko Miyazaki
Keyword(s):  
Air Conditioning ◽  
Low Cost ◽  
Freezing Temperature ◽  
Storage Life ◽  
Agricultural Products ◽  
Ambient Conditions ◽  
Humidity Control ◽  
Temperature And Humidity ◽  
Air Conditioning Systems ◽  
Term Storage

AbstractThe agricultural products are perishable in nature and possesses short shelf/storage life under ambient conditions. The temperature and humidity control systems are required to enhance to storage life of the products with optimum quality, quantity and nutritive attributes. In this regard, the significance of air-conditioning in storage application is highlighted along with the conventional storage options. The implications of compressor-based refrigeration and air-conditioning systems regarding low-cost and energy efficient air-conditioning systems are discussed in detailed. It is concluded that thermally driven air-conditioning systems can be used on top priority for the short-term storage of fresh agricultural products. Moreover, the long-term storage of products at freezing temperature can be made through hybrid systems instead of standalone conventional compressor based vapor compression refrigeration and/or air-conditioning systems. Finally, the air-conditioning systems are proposed for the optimum storage of different categorize of the food products.

Retrofitting low-cost heating ventilation and air-conditioning systems for energy management in buildings

2019 ◽  
Vol 236 ◽  
pp. 648-661 ◽  
Author(s):  
Syed Aftab Rashid ◽  
Zeeshan Haider ◽  
S.M. Chapal Hossain ◽  
Kashan Memon ◽  
Fazil Panhwar ◽  
...  
Keyword(s):  
Energy Management ◽  
Air Conditioning ◽  
Low Cost ◽  
Air Conditioning Systems

scholarly journals Analysis on The Risk of Respiratory Virus Transmission By Air Conditioning System Operation-Based on Experimental Evidence

2021 ◽  
Author(s):  
Yonghong Jia ◽  
Yue Xiang ◽  
Shurui Guo ◽  
Lei Guo ◽  
Luyao Guo ◽  
...  
Keyword(s):  
Air Conditioning ◽  
Respiratory Virus ◽  
Virus Transmission ◽  
Transmission Risk ◽  
Potential Health ◽  
Air Conditioning System ◽  
Medical Experiments ◽  
Epidemic Period ◽  
Central Air Conditioning ◽  
Air Conditioning Systems

Abstract It is important to know whether SARS-CoV-2 is spread through the air-conditioning systems. Taking the central air-conditioning system as an example, we analyze the mechanism and potential health risk of respiratory virus transmission in air-conditioned rooms, and propose a method to study the risk of virus transmission in central air-conditioning systems by investigating the data from medical experiments. The virus carrying capacity and the decay characteristics of indoor pathogen droplets are studied in this research. Additionally, the effects of air temperature and relative humidity on the virus survival in the air or on surfaces are investigated. The removal efficiency of infectious droplet nuclei by air-conditioning filter was then determined. Thus, the transmission risk during the operation of centralized air-conditioning system is evaluated. The results show that the indoor temperature and humidity are controlled in the range of 20-25℃ and 40%-70% by central air-conditioning during the epidemic period, which not only benefits the health and comfort of residents, but also weakens the vitality of the virus. The larger the droplet size, the longer the viruses survive. Since the filter efficiency of air-conditioning filter increases with the increase of particle size, increasing the number of air changes of the circulating air volume can accelerate the removal of potential pathogen particles. Therefore, scientific operation of centralized air conditioning systems during the epidemic period has more advantages than disadvantages.

Thermal Analysis of Low-Cost Dwellings in Mexico Using Greenroofs

2011 ◽  
Author(s):  
Mari´a G. Alpuche ◽  
Irene Marincic ◽  
Jose´ M. Ochoa ◽  
Hugo C. Moreno ◽  
Paloma Giottonini
Keyword(s):  
Energy Consumption ◽  
Air Conditioning ◽  
Low Cost ◽  
Concrete Block ◽  
Building Envelope ◽  
Air Cooling ◽  
Design Strategies ◽  
Cooling Systems ◽  
Air Conditioning Systems ◽  
Electricity Energy Consumption

According to the National Energy Balance (1), the electricity consumption in the residential and commercial sector represents thirty-three percent of the total consumed in the country. Most of the energy is consumed during the summer, when it is necessary to use air conditioning to maintain comfort conditions inside buildings. This aspect takes relevance in warm-dry climates, where a deficient design of building envelope and a wrong location of windows can increase the thermal loads producing an extra load to air conditioning systems and high costs by electricity energy consumption. For this reason, adequate design strategies and thermodynamic concepts have to be applied in order to make dwellings comfortable. Two dwellings are simulated and analyzed, the first one is made of regional materials like traditional concrete block walls, reinforced concrete roofs and economic finishes, the second one is proposed with a green roof and insulation in walls. The heat gains through the different constructive elements have been obtained, to analyze their impact on global thermal comfort and the electricity energy consumption of air cooling systems. Also, an exergy analysis has been applied to analyze exergy efficiency of air cooling systems and the influence that the building envelope can have in them with the proposed changes. The minimum exergy expenditure of air conditioning systems required to achieve comfort conditions inside dwellings could be a useful benchmark for the comparison of various dwelling designs.

ANALYSIS OF COMPETING VARIANTS OF AIR CONDITIONING SYSTEMS WITHOUT AIR EXTRACTION FROM ENGINES AT THE STAGE OF PASSENGER AIRCRAFT ONBOARD SYSTEMS CONCEPTUAL DESIGN

2019 ◽  
Vol 6 (3) ◽  
pp. 80-85
Author(s):  
Denis Igorevich Smagin ◽  
Konstantin Igorevich Starostin ◽  
Roman Sergeevich Savelyev ◽  
Anatoly Anatolyevich Satin ◽  
Anastasiya Romanovna Neveshkina ◽  
...  
Keyword(s):  
Conceptual Design ◽  
Air Conditioning ◽  
Research University ◽  
Cooling System ◽  
Fuel Efficiency ◽  
Air Cooling ◽  
Moscow Aviation Institute ◽  
Air Conditioning System ◽  
Low Efficiency ◽  
Air Conditioning Systems

One of the ways to achieve safety and comfort is to improve on-board air conditioning systems.The use of air cooling machine determines the air pressure high level at the point of selection from the aircraft engine compressor. Because of the aircraft operation in different modes and especially in the modes of small gas engines, deliberately high stages of selection have to be used for ensuring proper operation of the refrigeration machine in the modes of the aircraft small gas engines. Into force of this, most modes of aircraft operation have to throttle the pressure of the selected stage of selection, which, together with the low efficiency of the air cycle cooling system, makes the currently used air conditioning systems energy inefficient.A key feature of the architecture without air extraction from the main engines compressors is the use of electric drive compressors as a source of compressed air.A comparative analysis of competing variants of on-board air conditioning system without air extraction from engines for longrange aircraft projects was performed at the Moscow Aviation Institute (National Research University).The article deals with the main approaches to the decision-making process on the appearance of a promising aircraft on-board air conditioning system at the stage of its conceptual design and formulated the basic requirements for the structure of a complex criterion at different life cycle stages.The level of technical and technological risk, together with a larger installation weight, will require significant costs for development, testing, debugging and subsequent implementation, but at the same time on-board air conditioning system scheme without air extraction from the engines will achieve a significant increase in fuel efficiency at the level of the entire aircraft.

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